In a semiconductor manufacturing apparatus, particles sometimes adhere to a substrate, which is caused by dusts from a driving part of a transfer system for the substrate, reaction products peeled from an inner wall of a processing vessel and/or a substrate stage, mists during a liquid process, and so on. Thus, in order to evaluate a performance, a processing condition, and an operating condition of a semiconductor manufacturing apparatus, a condition of particles adhering to a substrate, which has been processed in the semiconductor manufacturing apparatus, is inspected by means of a particle inspecting apparatus.
As shown in FIG. 9A, in the particle inspection apparatus, light such as a laser beam is irradiated to a substrate 100, and an intensity of scattered light scattered by particles 101 on the substrate 100 is measured. Thus, the number of particles 101, sizes thereof and so on are measured.
The smaller the size of a particle 101 is, the weaker the scattered light from the particle 101 becomes. In this case, detection of the scattered light becomes difficult. In addition, since the substrate 100 has been subjected to various processes, the substrate 100 may be slightly undulated, or may have some Irregularities on a surface thereof. In this case, as shown in FIG. 9B, since a laser beam is also scattered on the surface of the substrate 100, it is impossible to distinguish between the scattered light that has been scattered on the surface of the substrate 100 and the scattered light that has been scattered by the particles 101 (error of measurement is significantly serious). This phenomenon becomes more conspicuous when the particles 101 are smaller in size.
For these reasons, it has been difficult to accurately detect the particles 101 smaller than, e.g., 0.03 μm.
It has been proposed that an Intensity of a laser beam to be irradiated is Increased so as to increase an intensity of scattered light from the particle 101. However, irradiation of the laser beam of such an increased intensity (output) is disadvantageous in that some particles 101 may explode (burn) and disappear by receiving the energy of the laser beam, and thus the particles cannot be detected.
JP9-186123A (particularly sections 0041 to 0044) proposes a method in which a mist of water is supplied to a cooled substrate so as to form an ice on the substrate around a particle as a base point. According to this method, a seeming size of the particle can be enlarged. (Subsequently, by blowing a gas under a high pressure to the surface of the substrate, the surface of the substrate is cleaned.) However, the inventors of the present invention have found that this method is disadvantageous in that the ice is also formed on regions of the surface of the substrate to which no particle adheres, so that a seeming amount of particles may be undesirably increased.
On the other hand, in order to cope with more minute patterns for the substrate, there is an ongoing demand for more accurately grasping (obtaining) an adhering condition of particles 101 that are more minute.